Conventionally, as described in Japanese Patent Application Laid-Open No. 2002-118981 and No. 2004-222376, a fuel cell system is known wherein a battery is connected in parallel with a fuel cell via a DC-DC converter that serves as a voltage converter.
According to Japanese Patent Application Laid-Open No. 2002-118981, the fuel cell system is mounted in a vehicle. Then, a fuel cell auxiliary equipment is connected between a DC-DC converter and a battery. With this arrangement, when an abnormality occurs in the DC-DC converter, the fuel cell auxiliary equipment continues to be driven by power received from the battery, and un-interrupted operation of the fuel cell is ensured.